Cook the beef filling

• Heat the oil in a frying pan over medium heat.
• Add the onion and garlic and cook until softened.
• Add the ground beef and break it up with a spatula until browned.

Season the filling

• Stir the taco seasoning and salt into the beef.
• Add a splash of water and simmer until the sauce thickens.

Prepare the toppings

• Dice the tomato, shred the lettuce and grate the cheddar.

Assemble the tacos

• Warm the taco shells.
• Fill each shell with the beef, then top with lettuce, tomato, cheddar and sour cream.